1. Field of the Invention
The present invention relates to a flat image display device and a method of manufacturing the image display device, and more particularly, to a flat image display device, having substrates opposed to each other and a plurality of electron sources arranged on the inner surface of one substrate, and a method of manufacturing the image display device.
2. Description of the Related Art
In recent years, there have been demands for image display devices for high-grade broadcasting or high-resolution versions therefor, which require higher screen display performance. To meet these demands, the screen surface must be flattened and enhanced in resolution. At the same time, the devices must be lightened in weight and thinned.
Accordingly, various flat image display devices have been developed as a next generation of light-weight, thin image display devices to replace cathode-ray tubes (hereinafter referred to as CRT). These image display devices include a liquid crystal display (hereinafter referred to as LCD), plasma display panel (hereinafter referred to as PDP), display device that utilizes the electroluminescence (EL) phenomenon of phosphors, field emission display (hereinafter referred to as FED), surface-conduction electron emission display (hereinafter referred to as SED), etc. In the LCD, the intensity of light is controlled by utilizing the orientation of a liquid crystal. In the PDP, phosphors are caused to glow by ultraviolet rays that are produced by plasma discharge. In the FED, phosphors are caused to glow by electron beams that are emitted from field-emission electron emitting elements. In the SED, which is a kind of an FED, phosphors are caused to glow by electron beams that are emitted from surface-conduction electron emitting elements.
For example, the SED has a first substrate and a second substrate that are opposed to each other with a given gap between them. Usually, these substrates are formed of a glass plate with a thickness of about 2.8 mm each, and have their respective peripheral edge portions joined together directly or by means of a sidewall in the form of a rectangular frame, thereby constituting a vacuum envelope. A phosphor layer that functions as an image display surface is formed on the inner surface of the first substrate. A large number of electron emitting elements for use as electron sources that excite the phosphors to luminescence are provided on the inner surface of the second substrate.
A plurality of spacers for use as support members are arranged between the first substrate and the second substrate in order to support atmospheric load that acts on these substrates. In displaying an image on this SED, an anode voltage is applied to the phosphor layer, and electron beams emitted from the electron emitting elements are accelerated and run against the phosphor layer by the anode voltage. Thereupon, the phosphor glows and displays the image.
According to the SED of this type, the size of each electron emitting element is on the micrometer order, and the distance between the first substrate and the second substrate can be set on the millimeter order. Thus, the SED, compared with a CRT that is used as a display of an existing TV or computer, can achieve higher resolution, lighter weight, and reduced thickness.
In the flat image display device of this type, as described above, a glass plate is used as each of the first and second substrates. In this case, however, it is hard to make the substrates thinner than the existing ones on account of strength problems. This constitutes a hindrance to further reductions in the thickness and weight of the image display device. Further, the strength problems of the glass substrates place many restrictions on the pitch, width, diameter, height dispersion, etc. of the spacers that are arranged between the first substrate and the second substrate, thereby retarding enhancement of precision and reduction in cost. Further, a glass plate, compared with a metal plate, entails more troublesome operations for working, formation, etc., and reduction of its manufacturing cost requires some countermeasure. As is generally known, glass plates easily break and are awkward to handle during manufacturing processes.